The present invention relates to a new and distinct variety of orange tree which will hereinafter be denominated varietally as "Chislett Summer Navel" orange tree and more particularly to an orange tree which produces fruit which are mature for harvesting and shipment approximately early spring in Kenley, Victoria, Australia and which further is distinguished principally as to novelty by producing large fruit which hang on the tree longer and with a higher internal flesh and external rind quality and color than the fruit of the "Late Lane Navel" orange tree.
The development of new varieties of citrus trees has not been as extensive as in the case of other families of fruit trees. In the United States, for example, while the sweet orange, known botanically as "Citrus sinensis", is typically a greater producer of fresh fruit by volume than any other fruit tree, the number of different varieties in production is significantly less than that of many other families of fruit trees. By way of illustration only, in the case of peach trees, the Register of New Fruit and Nut Varities, Second Edition, by Reid M. Brooks and H. P. Olmo, 1972, lists more than seven hundred varieties of peach trees in contrast to the just more than fifty varieties of orange trees. This disparity results, in part, from the susceptibility of many varieties of orange trees to diseases which are present in most of the citrus producing countries of the world. The infectious diseases are caused by bacteria, fungi and viruses and may, depending upon the specific type of disease, infect all portions of the trees. Accordingly, developmental work may be limited because of the prospect from expending enormous effort and time in the development of a new variety only ultimately to discover its susceptibility to a particular disease which destroys any significant commercial value therefor.
In any case, because of the comparative dearth of new varieties of orange trees, the discovery of new varieties having characteristics superior to those of known commercial varieties or having desirable ripening periods and a commercially acceptable resistance to disease is of event greater significance than in the case of other families of fruit trees. Where in addition, for example, the ripening period for a new variety of orange tree offers the prospect of fruit of high quality or otherwise attractive attributes later in the year than had theretofore been available in fruit of an equivalent character, the new variety is of noteworthy importance. The "Chislett Summer Navel" orange tree is such a variety.